The present invention concerns a novel antenna and, more particularly, an antenna for mounting on a glass plate with the radiator extending from one side of the glass plate and with the electrical wiring extending from the opposite side of the glass plate whereby energy is transferred through the glass plate and the drilling of a hole for coupling the radiator to the electrical wiring is unnecessary.
Vehicle owners are generally apprehensive about drilling holes in their vehicles and for that reason a window-mounted antenna which transfers RF energy through the glass is desirable. One prior art type of on-glass antenna is disclosed in U.S. Pat. No. 4,238,799. This prior art antenna utilizes a radiator that must be voltage fed, requiring the radiator to be an electrical half wavelength or multiples thereof. Since the feed point of the radiator is also the mounting point, this places the high impedance or high voltage point directly on the glass mounting surface.
While glass itself is a good low loss insulator, when rain and snow mix with contaminants such as dirt and salt are introduced on the glass surface, a serious degrading of performance will result because of the detuning and loss. This condition becomes worse as the frequency of operation is increased. In accordance with U.S. Pat. No. 4,238,799, in order to voltage feed the radiator, which is affixed to the outside of the glass, a coupling box containing an LC resonant circuit is attached to the inside of the glass. This resonant circuit inherently has some loss. The loss increases as this circuit becomes detuned.
It is an object of the present invention to provide an on-glass antenna that alleviates many of the problems concomitant with the prior art on-glass antenna disclosed in U.S. Pat. No. 4,238,799.
Another object of the present invention is to provide an on-glass antenna that is simple in construction and is easy to manufacture.
A further object of the present invention is to provide an on-glass antenna in which contaminants and water will have the least effect on performance and detuning.
A still further object of the present invention is to provide an on-glass antenna having a relatively wide band.
Other objects and advantages of the present invention will become apparent as the description proceeds.